A preliminary report on the Air India crash in June has found that both fuel control switches were in the cut-off position moments before the plane crashed in Ahmedabad.
Audio from the cockpit detailed in the report suggests confusion over the switches between the two pilots in the moments before the accident.
So how do fuel switches work and what role might they have played in the fate of flight 171? Our international business correspondent Theo Leggett explains.
This video has been updated to include additional information from the report.
